Franchitti fractured his spine, broke his right ankle and suffered a concussion in the Oct. 6 IndyCar crash

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Dario Franchitti, of Scotland, watches a warm up session for the IndyCar Grand Prix of Baltimore auto race, Sunday, Sept. 1, 2013, in Baltimore. Franchitti fractured his spine, broke his right ankle and suffered a concussion in the Oct. 6 crash.

Updated at 3:53 PM CDT on Thursday, Nov 14, 2013

Three-time Indianapolis 500 winner Dario Franchitti reluctantly retired Thursday after doctors told him it is too dangerous to continue racing following the injuries he suffered in a crash last month.

Franchitti fractured his spine, broke his right ankle and suffered a concussion in the Oct. 6 IndyCar race at Houston, where his car made contact with Takuma Sato's car on the last lap and sailed into a fence. Debris from the accident injured 13 fans in the grandstands and one IndyCar official.

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The 40-year-old Franchitti underwent two surgeries on his ankle and recently returned home to Scotland to recover.

"One month removed from the crash and based upon the expert advice of the doctors who have treated and assessed my head and spinal injuries post-accident, it is their best medical opinion that I must stop racing," Franchitti said. "They have made it very clear that the risks involved in further racing are too great and could be detrimental to my long term well-being. Based on this medical advice, I have no choice but to stop."

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The four-time IndyCar champion did not use the word "retire" in a lengthy statement released through Target Chip Ganassi Racing, the team he joined in 2009 following a brief stint in NASCAR with Ganassi a year earlier.

Franchitti was unstoppable upon his return to IndyCar. Teamed with Ganassi and driving the feared red No. 10 Target car, Franchitti reeled off three consecutive championships and won 12 races upon his return. Two of the wins were Indy 500s.

He became the face of the series and he always had crossover appeal for IndyCar through his 11-year marriage to actress Ashley Judd, which ended in January. But he was personable, well-spoken, popular in the paddock and passionate about the sport. It resonated with fans and made Franchitti one of IndyCar's all-time greats.

Franchitti's 31 victories are tied for eighth on the all-time list, and his 33 poles are sixth.

"Dario Franchitti has done so much for Target Chip Ganassi Racing, so it will be very disappointing to not see him in our cars next season," Ganassi said. "But simply put, Dario is a motorsports legend and will be sorely missed on the race track by everyone in the paddock and in the stands. His contributions to the sport of motor racing are too many to list, but I can tell you that they go way beyond what he has done on the track."

Franchitti's last victory was the 2012 Indy 500, an emotional race that came seven months after defending winner Dan Wheldon had been killed in a crash at Las Vegas. Franchitti battled teammate Scott Dixon over the final third of the race, jockeyed with Sato in the closing laps until Sato spun to bring out a caution, and led Dixon and Tony Kanaan across the finish line as three of Wheldon's closest friends finished 1-2-3.

It was a poignant moment for Franchitti, who was too familiar with death in the sport he loved. Best friend Greg Moore died in the 1999 season finale at Fontana, and Franchitti to this day remains deeply affected by the loss.

"I'll forever look back on my time racing in CART and the IndyCar Series with fond memories and the relationships I've forged in the sport will last a lifetime," he said. "Hopefully in time, I'll be able to continue in some off-track capacity with the IndyCar Series. I love open-wheel racing and I want to see it succeed. I'll be working with Chip to see how I can stay involved with the team, and with all the amazing friends I've made over the years at Target.

"As my buddy Greg Moore would say, 'See you up front' "

Juan Pablo Montoya, a longtime teammate of Franchitti's in the Ganassi organization on the NASCAR side, said he was disappointed Franchitti will not get a chance to return from his injuries. Montoya is moving to IndyCar next season to drive for Penske Racing.

"It's a shame that Dario had to finish his career like that, and I was looking forward to competing against him," Montoya said.

Target CEO Gregg Steinhafel praised Franchitti as one of the most exciting drivers in IndyCar, and also a strong brand ambassador.

"Not only has he had a storied career, but his popularity with Target's guests, his tremendous contributions to racing and his engagement in our community giving efforts have made him an integral part of Team Target," Steinhafel said.